Purpose: Allow user to create phonebook, add, delete, and modify contacts.
- Constructors: https://www.w3schools.com/java/java_constructors.asp
- Instance Variables: https://www.geeksforgeeks.org/variables-in-java/
- Java this keyword: https://www.w3schools.com/java/ref_keyword_this.asp
- Getters and Setters: https://www.w3schools.com/java/java_encapsulation.asp
- Chapter 16 Slides Deitel/Deitel LinkedLists
- https://www.geeksforgeeks.org/implementing-a-linked-list-in-java-using-class/
- https://www.javatpoint.com/java-list-node
- https://stackoverflow.com/questions/12617021/measure-size-length-of-singly-linked-list-in-java
- https://www.geeksforgeeks.org/introduction-to-doubly-linked-lists-in-java/
- Google AI search: "how to add at index singly linked list java"
- Google AI search "how to create linked list class java"